Issue 62

B. Kebaili et alii, Frattura ed Integrità Strutturale, 62 (2022) 14-25; DOI: 10.3221/IGF-ESIS.62.02

K EYWORDS . Recycled concrete; Waste recovery; Environment; Aggregates; Mechanical behavior.

I NTRODUCTION

A

lgeria is now undergoing a massive development program that includes nearly one million new homes, basic infrastructure, and a 1200 km east-west motorway [1,2]. This task necessitates the use of massive volumes of raw materials in concrete, road construction, and engineering fill, which harms the natural environment [3,4]. Concrete debris, which is generated by the demolition of old buildings and seismic disasters, has somehow been overlooked as a source of aggregate [5]. This waste is disposed as trash. Fig. 1 shows an uncontrolled landfill rubble discharge that affects the natural landscape.

Figure 1: Uncontrolled concrete waste dumping (Annaba, Algeria).

Reusing concrete waste as substitute aggregates would be a feasible solution to the aforementioned challenges, as well as a strategy to protect the environment by allowing for far more effective use of natural resources. Construction waste consumption in Algeria is 5%, with the remaining disposed of, providing a management and environmental policy issue [6]. The primary aim of this study is to show the potential benefits of employing concrete waste in the production of concrete. Recycled concrete aggregate (RCA) exhibited a wide variety of properties when compared to natural aggregate (NA). The percentage of RCA employed in concrete manufacturing varies from 25% to 100%; this range of replacement has been used to generate excellent recycled concrete. The substitution of natural aggregates by recycled aggregates in the production of fresh concrete provides a new aggregate supply while also allowing for the conservation of natural resources [6,7]. When 100 percent RCA was employed, the loss was determined by [8] to be decreased by roughly 20–25 percent when compared to normal concrete. Other research [7] observed a similar trend for strength to decline by roughly 8% when strength exceeds 60MPa. According to [9] the RCA has a high level of water absorption due to the porosity induced by the attached mortar, absorbing up to 8%. As a result, the RCA need more water to be as usable as NA. When crushed, RCA from low strength concrete has less attached mortar than RCA from high strength concrete as seen by [10]. When compared to NA, the increase in water content associated to RCA's porosity is thought to be responsible for the loss of compressive strength [11]. The water absorption coefficient may differ from the free water absorption calculated in the laboratory, and the pores of recycled aggregate are most likely filled with cement paste during mixing. This might result in an excess of water in the mixture [12]. Even when the fraction of coarse RCA replacement approaches 80 percent, structural concrete may be produced [10]. Some efficient and easy approaches, such as adjusting the water-cement ratio, aggregate water content, mixing technique, and additive [13], can enhance the concrete within a given range. Furthermore, increasing the cement content in recycled aggregate concrete (RAC) by around 6.2 percent without affecting the w/c ratio results in compressive strength and consistency comparable to that of ordinary concrete [14]. They also observed that compressive strength loss was just approximately 2.5 percent and 0.4 percent lower. According to [15], when RAC is mixed, a thin layer of cement slurry is generated on the surface, which penetrates through the porous attached mortar and fills cracks and voids. In the flexure strength it was found that the crack originated not just at the interfaces of the recycled aggregates and the mortar, but also at the RCA themselves [16]. Some studies revealed that the compressive strength of RAC decreased with

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